1. Field of the Invention
The present invention generally relates to testing of electronic devices, and more particularly a system and method for time domain reflectometry testing.
2. Description of the Related Art
Unless otherwise indicated herein, the approaches described in this section are not prior art to the claims in this application and are not admitted to be prior art by inclusion in this section.
Computer electronic components usually have to undergo a number of testing steps to ensure that they perform correctly. The time domain reflectometry (“TDR”) technique is one well-known testing method that is applied to characterize and locate faults in a conductive path of an electronic device. In this technique, a time domain reflectometer applies an input signal that is transmitted along a conductor in a device under test, and then detects a resulting reflection signal returned from the tested device. The reflection signal is a signal in function of time that is indicative of any discontinuities in the conductor impedance. To evaluate whether the device passes a requisite compliance test in the frequency domain, the detected signal is converted into frequency spectrum data, also called the return loss data, which are then compared against a predetermined level.
To illustrate, FIG. 1A is a simplified diagram of a conventional TDR testing setup 100. The testing setup 100 includes a TDR testing machine 110 that is coupled to a device under test 102 mounted on a printed circuit board (“PCB”) 104. The tested device 102 may include any computer electronic devices, such as a central processing unit, a graphics processing unit, chipset units, and the like. The testing machine 110 may be coupled to the tested device 102 via a suitable connector interface 106 provided for the tested device 102.
During testing, an end terminal 112 of the testing machine 110 applies an electric pulse signal that is transmitted to the tested device 102. Any impedance discontinuities along the transmission path of the inputted electric pulse signal will create echoes in a reflection signal returned by the tested device 102 and detected at the end terminal 112 of the testing machine 110. FIG. 1B is a schematic graph illustrating a graphic representation 120 of a reflection signal that may be measured at the end terminal 112. To determine whether the tested device 102 meets a standard requirement, the returned reflection signal is converted into return loss data, which are then compared against a predetermined threshold reference. FIG. 1C is a schematic graph illustrating corresponding return loss data 122 that are computed and compared against a threshold reference 124. If the return loss data 122 are entirely below the threshold reference 124, the tested device 102 complies with the standard requirement. Otherwise, the test has failed, and correction in the physical structure of the tested device 102 is needed.
While the aforementioned testing flow allows to generally determine the presence of defective conductor portions, it however fails to provide information helpful to the correction operation of the failed device 102. Even though the positions of certain distinctive peaks in the reflection signal 120 may be used to identify the defective portions that need reworking, another TDR test is still needed after the rework operation to ensure that all defects have been addressed. As a result, it is possible that multiple TDR testing and correction operations are needed before the tested device 102 successfully passes the compliance test, which increase the verification time and the labor cost as each correction requires a physical modification of the device 102.
Therefore, what is needed is an TDR testing system and method capable of providing information that will help in the correction operation of failed devices, and address at least the problems set forth above.